# US 2025/0095679 A1 · Magnetic disk device

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- Number: US 2025/0095679 A1
- Document ID: US20250095679A1
- Status: Published application
- Kind: A1
- Application number: 18/421,805
- Filed: 2024-01-24
- Published: 2025-03-20
- Earliest claimed: 2023-09-20
- Assignees: Kabushiki Kaisha Toshiba; Toshiba Electronic Devices & Storage Corporation
- Applicants: Kabushiki Kaisha Toshiba; Toshiba Electronic Devices & Storage Corporation
- Inventors: Takeyori HARA
- Web page: https://patentgrep.com/patent/US20250095679A1

## CPC

- G11B 5/59688: {Servo signal format patterns or signal processing thereof, e.g. dual, tri, quad, burst signal patterns}
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)

## Abstract

According to one embodiment, a magnetic disk device comprises a head position demodulation unit which demodulates a position of the head by performing switching between normal servo demodulation for processing servo information written to a servo sector of the disk and short servo demodulation for processing servo information by a short servo system, and a controller comprises a head position prediction unit which predicts a head position, and the head position prediction unit performs position prediction by using a latest head position obtained by demodulation by the head position demodulation unit and a head position obtained by past demodulation by normal servo demodulation.

## Claims

### Claim 1

A magnetic disk device comprising:
a disk;
a head;
a head position demodulation unit which demodulates a position of the head (head position) by performing switching between normal servo demodulation for processing servo information written to a servo sector of the disk and short servo demodulation for processing servo information by a short servo system; and
a controller which controls the position of the head, wherein
the controller comprises:
a head position prediction unit which predicts a head position; and
a write inhibition determination unit which determines that data write operation to the disk by the head is inhibited based on the predicted head position (head prediction position), and
the head position prediction unit performs position prediction by using a latest head position obtained by demodulation by the head position demodulation unit and a head position obtained by past demodulation by normal servo demodulation,
the controller further comprising:
a first position prediction unit which calculates a prediction position by a first calculation formula when the latest head position is a head position (normal head position) obtained by the normal servo demodulation; and
a second position prediction unit which calculates the prediction position by a second calculation formula which is different from the first calculation formula when the latest head position is a head position (short head position) obtained by the short servo demodulation.

### Claim 2

(canceled)

### Claim 3 (depends on 1)

The magnetic disk device of claim 1, wherein
the head position prediction unit performs switching between the first position prediction unit and the second position prediction unit.

### Claim 4 (depends on 1)

The magnetic disk device of claim 1, wherein
the first position prediction unit obtains the prediction position of the head using a velocity term of a position obtained by a difference between last two normal head positions.

### Claim 5 (depends on 1)

The magnetic disk device of claim 1, wherein
the second position prediction unit obtains the prediction position of the head using a velocity term of a position obtained by a difference between last two normal head positions.

### Claim 6 (depends on 5)

The magnetic disk device of claim 5, wherein
the second position prediction unit obtains a plurality of differences between past normal head positions and obtains the prediction position of the head using a weighted average of the differences.